The response was overwhelmingly negative. While some readers criticised her for feeding her child in a store, many zeroed in on the contents of the sandwich.

"That's really inconsiderate," one person wrote. "So many kids have life threatening allergies to peanut butter. Eating it in a shopping cart GUARANTEES it will be smeared on the handle, etc. It's really awful you would do this."

Others called her "kind of lousy", the "epitome of low brow", "the worst kind of person", "awful", "so gross... it needs to be fake" and "disgusting".

One commenter even questioned whether she was a real mother, and another said "snacking culture is completely out of control".

It's estimated around 0.5 percent of adults have a peanut allergy, but it could be as high as 6 to 7 percent in children, and rising.

Many schools and daycares now ban products containing peanuts. In recent years, scientists have begun to find ways to reduce the severity of allergic reactions to peanuts, but it's still not clear what causes it in the first place.

A few respondents on UrbanBaby backed the mother, saying it was up to parents of children with allergies to monitor their children's environment, rather than ban everyone else from eating peanuts.

"It isn't our role as a parent to police other parents children or to keep them safe from harm. It isn't our role to ensure that a random person's child doesn't come into contact with an item they may be allergic to."

"You peanut-allergy freaks are exactly what's wrong with the world these days. You shitty parents put your kids into a bubble and then expect everyone else to bow down to your allergic snowflake brat kids that YOU caused. It is YOUR FAULT your brat kids have allergies. Please keep them home in their bubble and away from NORMAL kids!!"

If an allergic person comes into contact with a peanut, they can break out in hives, get really itchy, feel nauseous or even go into life-threatening anaphylactic shock.